Archive for the ‘Personal’ category

I have arrived back in Waterloo to start my new hybrid University/Perimeter Institute position. It’s been quite a long break from posting, because – strangely enough – having two affiliations means I had to do twice the amount of paperwork to get myself set-up this time. As much as I loved being at PI, it is nice to be back in a university and to have some small role in educating the next generation of quantum mechanics.

Over the break, Andrew Thomas has left a few comments about the role of decoherence in interpretations of quantum theory in my Professional Jealousy post. There are some who think that understanding decoherence alone is enough to “solve” the conceptual difficulties with quantum theory. This is quite a popular opinion in some quarters of the physics community, where one often finds people mumbling something about decoherence when asked about the measurement problem. However, there are also many deep thinkers on foundations who have denied that decoherence completely solves the problems, and I tend to agree with them, so we’ll have a post on “What can decoherence do for us?” later on this week.

To clarify, I’m not going to argue that decoherence isn’t an important and real physical effect, nor am I going to say that it has no role at all in foundational studies, so please hold your fire until after the next post if you were thinking of commenting to that effect.

As I don’t expect to be able to blog again before the Xmas break, I’d like to wish all readers of QQ a happy whateveryou’recelebrating.

The holidays are one of those times of year when relatives get the opportunity to ask you, “So, what exactly is it that you do research on?”. This dreaded question will come with certainty, regardless of how many times you have previously explained it to them. It’s not their fault because the average person does not have physics on their mind for any significant amount of time, so it’s easy to forget what it’s all about.

The question is especially bad if you spend any time thinking about the foundations of quantum theory, because it’s difficult to describe quantum theory accurately in a few words. Here’s my best shot at an answer at the moment.

Miscellaneous Relative: So, what is this quantum theory thing all about then?

Me: Well, it’s not exactly about the fact that particles sometimes behave like waves and waves like particles.

MR: Go on.

Me: There is this thing called the Heisenberg uncertainty relation, but strictly speaking it doesn’t say that a measurement of position necessarily disturbs the momentum and vice-versa.

MR: OK.

Me: And it’s definitely not that there are multiple universes.

MR: That’s a shame. I enjoy science fiction, so that was the bit I liked the most.

Me: There are these things called wavefunctions, which can be in superpositions, but it’s not entirely clear what the true significance of that is.

MR: I’m not getting much insight into what you actually do from this by the way.

Me: It seems that John Bell proved that locality and realism are incompatible, but people are still debating the significance of that, so it’s definitely not the whole story either.

MR: Now I really have no clue what you are talking about.

Me: It’s not just about “finding the right language” with which to talk about physics. In particular, I don’t think that revising logic is really the right thing to do.

MR: That sounds sensible enough.

Me: Some people think the whole thing is just about doing something called “solving the measurement problem”, but I don’t think that’s an entirely helpful way of looking at things.